Semiconductor Device Packaging Assembly, Lead Frame Strip and Unit Lead Frame with Trenches or Grooves for Guiding Liquefied Molding Material

ABSTRACT

A unit lead frame includes a periphery structure, a die paddle inside of the periphery structure, a plurality of leads extending between the periphery structure and the die paddle, and trenches or grooves extending from an outer surface of the periphery structure and configured to guide liquefied molding material onto the periphery structure along sidewalls of the trenches or grooves.

TECHNICAL FIELD

The instant application relates to lead frame strips, and moreparticularly to physical supporting encapsulated semiconductor diesduring processing of lead frame strips.

BACKGROUND

A lead frame forms the base or skeleton of an IC package, providingmechanical support to semiconductor dies during assembly into a finishedpackage. A lead frame typically includes a die paddle for attaching asemiconductor die, and leads providing the means for external electricalconnection to the die. The die can be connected to the leads by wires,e.g., through wire bonding or tape automated bonds. Lead frames aretypically constructed from an electrically conductive material, such ascopper or aluminum. The electrically conductive material may be providedin the form of a flat sheet metal. The features of the lead frames maybe defined by forming openings in the flat sheet metal. The flat sheetmetal can be patterned with a plurality of identically openings so as toform lead frame strips, i.e., interconnected strips used to package anumber of semiconductor dies in a common process. Each lead frame stripincludes a number of unit lead frames, with each unit lead frame havingthe die paddle and lead construction described above.

After completion of the assembly process, semiconductor dies attached tothe die paddles are usually tested after separation of the unit leadframes from the lead frame strip, e.g., by punching. In other words, thesemiconductor dies can be individually tested after singulation of theunit lead frames. Alternatively, the packaged semiconductor dies may betested while still being physically supported by the lead frame stripusing tie bars. This is commonly referred to as lead frame striptesting. In this technique, separation of the unit lead frames from thelead frame strip occurs after lead frame strip testing. However, the tiebars are formed from the same material as the die paddle, and are partof the unit lead frames. This is problematic for applications in whichthe die paddles serve an electrical connection function, e.g., in DSO(dual small outline) packages in which the exposed die paddles providean electrical connection to the backside of semiconductor dies attachedto the die paddles. In this case, the tie bars electrically short thedie paddles to the lead frame strip and to other die paddles attached tothe same lead frame strip, complicating the electrical testing process.Electrical isolation is also required for other lead frame processingsuch as partial plating and electrical charge processes.

SUMMARY

A method of processing a lead frame strip having a plurality of unitlead frames is disclosed. Each of the unit lead frames has a peripherystructure connecting adjacent ones of the unit lead frames, a die paddleinside of the periphery structure, a plurality of leads connected to theperiphery structure and extending towards the die paddle, and a moldingcompound channel in the periphery structure configured to guideliquefied molding material. According to an embodiment, the methodincludes attaching a semiconductor die to each of the die paddles,electrically connecting the semiconductor dies to the leads, and forminga liquefied molding compound on each of the unit lead frames. Theliquefied molding compound is formed such that the liquefied moldingcompound encapsulates the semiconductor dies and flows into the moldingcompound channels thereby forming molding extensions that extend ontothe periphery structures.

A method of forming a lead frame strip for packaging a plurality ofsemiconductor dies is disclosed. According to an embodiment, the methodincludes forming a plurality of connected unit lead frames, each of theunit lead frames including a periphery structure connecting adjacentunit lead frames in the lead frame strip, a die paddle inside of theperiphery structure, and a plurality of leads connected to the peripherystructure and extending towards the die paddle. The method furtherincludes forming a molding compound channel in each of the peripherystructures, each of the molding compound channels being configured toguide liquefied molding material so as to form molding extensions thatextend onto the periphery structures.

A semiconductor device packaging assembly is disclosed. According to anembodiment, the semiconductor device packaging assembly includes a leadframe strip having a plurality of unit lead frames. Each of the unitlead frames include a periphery structure connected to adjacent ones ofthe unit lead frames, a die paddle inside of the periphery structure, aplurality of leads extending between the periphery structure and the diepaddle, and a molding compound channel in the periphery structure. Themolding compound channel is configured to guide liquefied moldingmaterial onto the periphery structure.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The elements of the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding similarparts. The features of the various illustrated embodiments can becombined unless they exclude each other. Embodiments are depicted in thedrawings and are detailed in the description which follows.

FIG. 1 illustrates a plan view of a lead frame strip with moldingcompound channels formed in the periphery structure of each unit leadframe in the lead frame strip, according to an embodiment.

FIG. 2, which includes a plan view in FIG. 2A and a cross-sectional viewin FIG. 2B, illustrates an enlarged view of the molding compoundchannels, according to an embodiment.

FIG. 3 illustrates a plan view of a lead frame strip with semiconductordies affixed to the die paddles and a molding compound encapsulating thesemiconductor dies, according to an embodiment.

FIG. 4, which includes FIGS. 4A and 4B, illustrates an enlarged view ofthe molding compound extending into the molding compound channels andforming molding extensions on the periphery structure, according todifferent embodiments.

FIG. 5 illustrates the lead frame strip after trimming the leads,according to an embodiment.

FIG. 6 illustrates a cross-sectional configuration of the moldingcompound channels, according to an embodiment.

FIG. 7 illustrates a cross-sectional configuration of the moldingcompound channels, according to another embodiment.

FIG. 8 illustrates a cross-sectional configuration of the moldingcompound channels, according to another embodiment.

FIG. 9 illustrates a cross-sectional configuration of the moldingcompound channels, according to another embodiment.

FIG. 10, which includes FIG. 10A and FIG. 10B, illustrates a two-stepprocess of forming the molding compound channels of FIG. 9, according toan embodiment.

DETAILED DESCRIPTION

Embodiments disclosed herein include a lead frame strip with a pluralityof unit lead frames. Each unit lead frame includes a periphery structure(e.g., a ring-like structure) connecting adjacent ones of the unit leadframes, a die paddle inside of the periphery structure, and a pluralityof leads connected to the periphery structure and extending towards thedie paddle. Molding compound channels are formed in the peripherystructure of each unit lead frame. According to an embodiment, theperiphery structure of each unit lead frame includes tabs extendingtowards the lead frame, and the molding compound channels are formedalong these tabs. The molding compound channels have a trench structuresuch that liquefied molding material is guided through the channels.During encapsulation of the semiconductor dies, liquefied moldingmaterial flows into the channels thereby forming molding extensions thatextend onto the periphery structures. These molding extensions may havea finger like structure, for example.

Advantageously, the lead frame strip configuration and methods describedherein provide a mechanism to physically support the die paddles andcorrespondingly attached semiconductor dies using the molding material.This allows for further processing steps (e.g., lead frame striptesting) to be performed after the lead trim and before singulation ofthe encapsulated semiconductor dies. According to an embodiment, theencapsulated semiconductor dies are only physically connected to theperiphery structures by portions of the molding compound that includethe molding extensions. That is, the die paddles are not connected tothe periphery structures by a tie bar and there is no electricalconnection between the die paddles and the periphery structures. Thus,strip-level testing of multiple encapsulated semiconductor dies can beperformed, and this testing can be applied to each terminal of thesemiconductor dies, including the terminal that is connected to the diepaddles.

Referring to FIG. 1, a plan view of a lead frame strip 100 is depicted,according to an embodiment. The lead frame strip 100 includes aplurality of unit lead frames 102, two of which are depicted in FIG. 1.Each of the unit lead frames 102 has a periphery structure 104 (e.g., aring-like structure) connecting adjacent ones of the unit lead frames102 together. Each of the unit lead frames 102 additionally includes adie paddle 106 inside of the periphery structure 104. In the event thatthe periphery structure 104 is formed as a closed loop, the die paddle106 is completely surrounded by the periphery structure 104. The diepaddle 106 may have a rectangular shape, for example. The unit leadframes 102 further include a plurality of leads 108 connected to theperiphery structure 104 and extending towards the die paddle 106. Someof the leads 108 may be connected to the die paddle 106 as well.

The configuration of the unit lead frames 102 (e.g., the number anddimensions of the leads 108, size of the die paddle 106, etc.) may vary,depending upon the desired configuration of the finalized packagedesign. Exemplary package designs include the SCT595 and SOT223packages. The unit lead frames 102 may be formed along a single plane.Alternatively, the unit lead frames 102 may be formed along more thanone plane. For example, the die paddle 106 may be vertically offset fromthe periphery structure 104.

The lead frame strip 100 may be formed by providing a sheet layer ofelectrically conductive material (e.g., copper, aluminum and the like)and by forming openings 110 in the sheet metal, e.g., by stamping oretching. According to an embodiment, the openings 110 are formed byphotolithography. The geometry of the openings 110 defines the featuresof the unit lead frames 102, including the die paddle 106, the peripherystructure 104, and the leads 108. A plurality of lead frame strips 100may be formed from a single sheet, and the individual strips 100 may besingulated (i.e., separated) from this sheet.

According to an embodiment, each unit lead frame 102 includes one ormore tie bars 112 connecting the die paddle 106 to the peripherystructure 104. The tie bar 112 may be part of the sheet metal used toform the lead frame strip 100. Thus, the tie bar 112 provides a metallicconnection between the die paddle 106 and the periphery structure 104that is separate from the leads.

The tie bars 112 are represented by dashed lines because they areoptional. According to an embodiment, the tie bars 112 re not includedin the unit lead frames 102. In this embodiment, the leads 108 providethe only connection between the die paddles 106 and the adjacentperiphery structure 104. According to the embodiment of FIG. 1, the diepaddle 106 is physically connected (and supported) by two leads 108 onopposite sides of the die paddle 106. These leads 108 may form the powersupply leads 108 in the packaged device, for example.

Each of the unit lead frames 102 includes a molding compound channel 114in the periphery structure 104. According to an embodiment, the moldingcompound channels 114 are formed on a pair of opposite facing tabs 116of the periphery structure 104 that extend towards the die paddles 106.The arrangement of the tabs 116 and/or molding compound channels 114 mayvary.

Referring to FIG. 2, an enlarged view of the tabs 116 having the moldingcompound channels 114 is depicted. FIG. 2A depicts a plan-view of thetabs 116 and molding compound channels 114 and FIG. 2B depicts across-sectional view of the tabs 116 and molding compound channels 114along the line A-A′ depicted in FIG. 2A. The molding compound channels114 are configured to guide liquefied molding material. For example, themolding compound channels 114 may be formed as trenches or groovesextending from an outer surface 118 of the periphery structures 104 ineach unit lead frame 102. These trenches or grooves are deep and wideenough such that liquefied molding material (e.g., a thermosettingplastic) will enter the molding compound channels 114 and will be guidedsidewalls of the channels 114. Furthermore, the molding compoundchannels 114 increase the available surface area of the peripherystructure 104 thereby improving adhesion between the molding materialand the unit lead frames 102. The number, length and depth of themolding compound channels 114 may be adjusted according to theseconsiderations. The molding compound channels 114 are intentionallyformed into the unit lead frames 102, and are larger than naturallyoccurring impressions or indentations. Specific cross-sectionalconfigurations of the molding compound channels 114, and techniques forforming the molding compound channels 114, will described in furtherdetail with reference to FIGS. 6-10.

Referring to FIG. 3, a method of processing the lead frame strip 100 isshown. According to the method, a semiconductor die 120 has beenattached to the die paddles 106 in each of the unit lead frames 102. Thesemiconductor dies 120 may be attached by a solder material or adhesive,for example. After die attachment, the semiconductor dies 120 areelectrically connected to the leads 108. For example, wire bonds or tapeautomated bonds may be provided between a top side of the semiconductordies 120 and the leads 108. In the embodiment of FIGS. 3, the lowersides of the semiconductor die 120 is electrically connected to two ofthe leads 108 via the die paddle 106 to provide a source connection.

The method further includes forming a liquefied molding compound 122 oneach of the unit lead frames 102 such that the liquefied moldingcompound 122 encapsulates the semiconductor dies 120. This may be doneusing any of a number of known encapsulation techniques that utilizeliquefied molding material. The molding compound 122 is an electricallyinsulating material, and may be a thermosetting epoxy resin or athermoplastic, for example. According to an embodiment, encapsulation ofthe semiconductor dies 120 is done using a transfer molding process. Inthis technique, a mold cavity is placed on each unit lead frame 102 suchthat the die paddle 106 and the corresponding semiconductor die 122attached to the die paddle 106 are arranged inside of the mold cavity.Thereafter, the liquefied molding compound 122 is transferred into themold cavity (e.g., through a mold gate). The mold cavity adjoins themolding compound channels 114 so that the liquefied molding compound 122may enter the mold cavity. According to an embodiment, the liquefiedmolding compound 122 enters the mold cavity and fills up the moldingcompound channels 114.

An enlarged view of the lead frame strip 100 in region “B” is depictedin FIG. 4. The molding process is performed such that the liquefiedmolding compound 122 flows into the molding compound channels 114thereby forming molding extensions 124 that extend onto the peripherystructures 104.

FIG. 4 provides a detailed view of the molding extensions 124. Themolding extensions 124 correspond to portions of the molding compound112 that are guided by the molding compound channels 114, and remain inthe molding compound channels 114 after the molding process.

FIG. 4A depicts an embodiment in which the mold cavity is configuredsuch that (within process tolerances) edges 130 of the molding compound122 do not extend over the tabs 116. That is, the only portions of themolding compound 122 that are arranged on or extend over the unit leadframe 102 are the molding extensions 124.

FIG. 4B depicts an alternate embodiment in which the edges 130 moldingcompound 122 overlap with the tabs 116. That is, FIG. 4B depicts anovermold configuration. In this embodiment, the mold cavity may beplaced over the tabs 116 of the periphery to form a rectangular portionof the molding compound 122 that is supported by the tabs 116.

After forming the liquefied molding compound 122 in the manner describedabove, the molding compound 122 is hardened. For example, if the moldingcompound 122 is a thermosetting epoxy resin or a thermoplastic, the leadframe strip 100 is cooled to cause the liquefied molding compound 122 totransition to a solid state or a partially solid state. As a result, thesemiconductor dies 120 are encapsulated by an electrically insulatingmolding structure 126. Furthermore, the encapsulated semiconductor dies120 are secured to the adjacent periphery structures 104 by sections ofthe hardened molding structure 126 including the molding extensions 124.That is, the die paddles 106 and correspondingly attached semiconductordies 120 are physically coupled to the adjacent periphery structures 104by sections of the hardened molding structure 126 that adhere tocoupling points, i.e., the tabs 116 of the periphery structures 104 thatinclude the molding compound channels 114. The presence of the moldingcompound channels 114 and the corresponding molding extensions 124provides a high degree of adhesion between the hardened molding compoundand the unit lead frame 102. Furthermore, the molding compound channels114 and the corresponding molding extensions 124 provide an extendedsurface area to distribute the weight of the encapsulated semiconductordies 120. As a result, a secure and reliable connection between hardenedmolding structure 126 and the unit lead frame 102 is formed.

According to an embodiment, the hardened molding structure 126 has arectangular portion. That is, the molding structure 126 has first edgesides 128 that are parallel to one another and second edge sides 130that are parallel to one another and perpendicular to the first edgesides 128. The leads 108 may be perpendicular to the first edge sides128. The second edge sides 130 extend at least to the edge side of thetabs 116 that include the molding compound channels 114.

In the configuration of FIG. 4A, the molding extensions 124 provide theexclusive physical support mechanism between the unit lead frame 102 andthe molding structure 126. In the overmold configuration of FIG. 4B, theoverlap region provides further physical support (in addition to thephysical support provided by the molding extensions 124) between theunit lead frame 102 and the molding structure 126. However, the tabs 116are not necessarily part of the finalized package structure. When theencapsulated semiconductor dies 120 are eventually singulated to formindividual packaged semiconductor devices, the molding structure 126 canbe cut along a scribe line S that is spaced apart from the tabs 116,between the tabs 116 and the die paddle 106. In other words, the processcan be controlled so that the molding structure is devoid of anymetallic components at the edge sides corresponding to remnant portionsof the tabs 116.

According to an embodiment, the molding extensions 124 are configured asfingers that extend away from the second edge sides 130 of therectangular shaped portion of the molding structure. That is, aplurality of rectangular shaped molding extensions 124 that are parallelto one another extend outside of the rectangular shaped portion of themolding structure 126, perpendicular to the second edge sides 130.

Referring to FIG. 5, after hardening of the molding compound 122, theconnections between the leads 108 and the periphery structures 104 ineach of the unit lead frames 102 are severed. According to anembodiment, every continuous metallic connection between the die paddles106 and the periphery structures 104 in each unit lead frame 102 issevered. In other words, there is no tie bar 112 or lead 108 physicallycoupling the die paddles 106 to the periphery structure 104. Theseconnections may be severed by a lead trim process. If the unit leadframes 102 include the optional tie bar 112, this connection may besevered as well. As a result, the die paddle 106 and leads 108 areelectrically disconnected from the periphery structure 104. Further,portions of the molding structure 126 including the molding extensions124 provide the only physical support mechanism between the encapsulatedsemiconductor dies 120 and the periphery structures 104 in each unitlead frame 102. That is, the die paddle 106 is electrically insulatedfrom the periphery structure 104, but remains physically supported bythe periphery structure 104.

After severing the connections, further processing steps can beperformed on the lead frame strip 100. These processing steps mayinclude lead frame strip 100 testing, partial plating, and electricalcharging, for example.

Advantageously, because the tie bar 112 can be eliminated, electricalaccess to each of the device terminals is possible, including anyterminals connected to the die paddle 106, during these furtherprocessing steps. That is, the portions of the hardened moldingstructure 126 that include the molding extensions 124 provide thenecessary physical support of the encapsulated semiconductor dies 120such that a tie bar 112 is no longer needed to perform strip-leveltesting.

A further advantage of eliminating the tie bar 112 is that the finalizedpackaged device is less susceptible to corrosion and delamination. In atie bar design, when the finalized package is singulated by cutting themolding structure along a splice line (e.g., in the manner describedabove), the finalized package includes a remnant of the tie barextending from the die paddle to an edge side of the package. Thiscreates a path for chemical corrosion between the exterior and theinterior of the package and therefore increases the likelihood offailure. In addition, this path increases the possibility that themolding structure 126 will delaminate (i.e., separate). By contrast, thelead frame strip 100 design disclosed herein allows for the hardenedmolding structure 126 to be cut along the splice line S (shown in FIGS.4A and 4B) between the tabs 116 and the die paddle 106 such that an edgeside of the finalized package where the hardened molding structure 126has been spliced is substantially devoid of metallic material (e.g.,from the tie bar 112 or the tabs 116). In other words, the path forchemical corrosion described above can be eliminated. Further, this thiscan be done without forfeiting the benefits of lead frame strip testing.

According to an alternate embodiment, at least one continuous metallicconnection between the die paddles 106 and the periphery structure 104remains in each unit lead frame 102 after severing the connectionsbetween the leads 108 and the periphery structures 104. For example,each unit lead frame 102 may include one or more tie bars 112, and thesetie bars 112 are not severed during the trimming of the leads 108.

After severing the connections between the leads 108 and the peripherystructures 104, the tie bar 112 forms the only continuous metallicconnection between the die paddle 106 and the periphery structure 104 ineach unit lead frame 102. In the alternative, one of the leads 108 maynot be trimmed. In either case, the portions of the hardened moldingstructure 126 including the molding extensions 124 advantageouslyprovide additional physical support and adhesion between the hardenedmolding structure 126 and the periphery structure 104 in the mannerpreviously discussed.

FIGS. 6-9 depict possible cross-sectional geometries of the moldingcompound channels 114. FIGS. 6-9 each depict the unit lead frames 102along the cross-sectional line A-A′ shown in FIG. 4.

As shown in FIG. 6, the molding compound channels 114 may have a v-shapecross-sectional geometry. As a result, the counterpart moldingextensions 124 formed in the channels 114 act as teeth that engage withthe unit lead frames 102.

As shown in FIG. 7, the molding compound channels 114 may have a u-shapecross-sectional geometry. That is, the molding compound channels 114include linear sidewalls and a bottom section that forms an obtuse orperpendicular angle with the linear sidewalls.

FIG. 8 depicts an embodiment in which the molding compound channels 114are formed on opposite facing surfaces 118 of the periphery structure104 such that the molding extensions 124 extend over both of theseopposite facing outer surfaces 118. This configuration providesadditional adhesion between the hardened molding structure 126 and theunit lead frame 102. In addition, this configuration allows the leadframe strip 100 to be tilted while maintaining physical support of theencapsulated semiconductor dies 120. The u-shaped geometry for themolding extensions 124 is used as an example. However, alternategeometries are possible for the molding extensions 124, including theexemplary geometries disclosed herein.

FIG. 9 depicts and embodiment in which the molding compound channels 114have two cross-sectional regions 132, 134. In a vertical direction (V)perpendicular to an outer surface 118 of the periphery structure 104,the molding compound channels 114 narrow in the first cross-sectionalregion 132. In the same vertical direction (V), the molding compoundchannels 114 widen in the second cross-sectional region 134.Consequently, the molding extensions 124 interlock with thecorresponding molding compound channels 114. That is, the moldingextensions 124 engage with the sidewalls of the molding compoundchannels 114 such that the sidewalls resist physical forces applied bythe molding extensions 124 in the vertical direction (V). As a result,the adhesion and resistance to mechanical forces provided by the moldingextensions 124 is increased. According to an embodiment, at a transitionbetween the two cross-sectional regions 132, 134, a sidewall portion 136of the molding compound channels 114 is substantially parallel to theouter surface 118.

The molding compound channels 114 may be formed by a punching process,for example. For example, after providing the sheet layer ofelectrically conductive material and forming openings 110 in the sheetmetal that define the features of each unit lead frame 102, the outersurface 118 of the electrically conductive material may be punched ineach unit lead frame 102. A pair of opposite facing molding compoundchannels 114 may be formed along opposite facing surfaces 118 (e.g., themolding compound channels 114 depicted in FIG. 8) by punching both ofthe opposite facing surfaces 118, either sequentially or simultaneously.As a result, pairs of opposite facing molding compound channels 114 thatare spaced apart from one another by a thinned portion of theelectrically conductive material that remains after the molding compoundchannels 114 are formed. As an alternative to punching, other techniquesmay be utilized to form the molding compound channels 114, e.g.,etching, stamping, coining, etc.

FIG. 10 depicts a two-step punch process that may be used to form themolding compound channels 114. This two-step punch process may be usedto form the cross-sectional configuration of FIG. 9, for example. FIG.10A depicts a first punching step of the process in which the outersurface 118 is punched to form channels with linear sidewalls 138extending away from the outer surface 118 to a bottom of the channels.FIG. 10B depicts a second punching step in which the sidewalls 138 aremodified so as to form angles between the outer surface 118 and thebottom of the channels. This may be done by performing a wider andshallower punch in the second punch step than in the first punch step.Subsequently, an interlocking molding extension 124 may be formed in thechannel 114 in the manner previously discussed.

The term “substantially” encompasses absolute conformity with arequirement as well as minor deviation from absolute conformity with therequirement due to manufacturing process variations, assembly, and otherfactors that may cause a deviation from the ideal. Provided that thedeviation is within process tolerances so as to achieve practicalconformity, the term “substantially” encompasses any of thesedeviations. For example, “substantially parallel” surfaces may bedeviate from one another by up to five degrees.

Spatially relative terms such as “under,” “below,” “lower,” “over,”“upper” and the like, are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the device in additionto different orientations than those depicted in the figures. Further,terms such as “first,” “second,” and the like, are also used to describevarious elements, regions, sections, etc. and are also not intended tobe limiting. Like terms refer to like elements throughout thedescription.

As used herein, the terms “having,” “containing,” “including,”“comprising” and the like are open-ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a,” “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

With the above range of variations and applications in mind, it shouldbe understood that the present invention is not limited by the foregoingdescription, nor is it limited by the accompanying drawings. Instead,the present invention is limited only by the following claims and theirlegal equivalents.

What is claimed is:
 1. A unit lead frame, comprising: a peripherystructure; a die paddle inside of the periphery structure; a pluralityof leads extending between the periphery structure and the die paddle;and molding compound channels formed in the periphery structure andconfigured to guide liquefied molding material onto the peripherystructure, the molding compound channels being formed in tabs of theperiphery structure, the tabs extending towards the die paddle.
 2. Theunit lead frame of claim 1, further comprising a tie bar connecting thedie paddle to the periphery structure.
 3. The unit lead frame of claim1, wherein the molding compound channels are formed on opposite facingouter surfaces of the periphery structure.
 4. The unit lead frame ofclaim 1, wherein in a vertical direction perpendicular to an outersurface of the periphery structure, the molding compound channels narrowin a first cross-sectional region and widen in a second cross sectionalregion.
 5. The unit lead frame of claim 4, wherein a sidewall portion ofthe molding compound channels extends in a direction that issubstantially parallel to the outer surface.
 6. A lead frame strip,comprising: a plurality of unit lead frames; a periphery structureconnected to adjacent ones of the unit lead frames; a die paddle insideof the periphery structure in each unit lead frame; a plurality of leadsextending between the periphery structure and each of the die paddles;and a pair of opposite facing molding compound channels formed alongopposite facing surfaces of each unit lead frame in the peripherystructure and configured to guide liquefied molding material onto theperiphery structure, the opposite facing molding compound channels ofeach pair being spaced apart from one another by a thinned portion ofelectrically conductive material of the periphery structure.
 7. The leadframe strip of claim 6, wherein each of the unit lead frames furthercomprises a tie bar connecting the corresponding die paddle to theperiphery structure.
 8. The lead frame strip of claim 6, wherein in eachof the unit lead frames, the molding compound channels are formed onopposite facing outer surfaces of the periphery structure.
 9. The leadframe strip of claim 6, wherein in a vertical direction perpendicular toan outer surface of the periphery structure, the molding compoundchannels narrow in a first cross-sectional region and widen in a secondcross sectional region.
 10. The lead frame strip of claim 9, wherein asidewall portion of the molding compound channels extends in a directionthat is substantially parallel to the outer surface.
 11. A unit leadframe, comprising: a periphery structure; a die paddle inside of theperiphery structure; a plurality of leads extending between theperiphery structure and the die paddle; and trenches or groovesextending from an outer surface of the periphery structure andconfigured to guide liquefied molding material onto the peripherystructure along sidewalls of the trenches or grooves.
 12. The unit leadframe of claim 11, further comprising a tie bar connecting the diepaddle to the periphery structure.
 13. The unit lead frame of claim 11,wherein the trenches or grooves are formed on opposite facing outersurfaces of the periphery structure.
 14. The unit lead frame of claim11, wherein in a vertical direction perpendicular to the outer surfaceof the periphery structure, the trenches or grooves narrow in a firstcross-sectional region and widen in a second cross sectional region. 15.The unit lead frame of claim 14, wherein the sidewalls of the trenchesor grooves extend in a direction that is substantially parallel to theouter surface.